TITLE: Dysregulated Adenosine Methylation of mRNA as a Novel Mechanism of Heart Failure PROJECT SUMMARY: One of most exciting advancements in the RNA field is the recent discovery that post-transcriptional modifications of mRNAs (epitranscriptome) are vital to several cellular processes including mRNA stability, nuclear export, cellular compartmentalization, splicing, translation and their degradation. However, function of the epitranscriptome remains unexplored in mature post-mitotic tissues such as the mammalian heart especially under the pathophysiological remodeling. Discrepancies in expression levels of mRNAs and proteins in the hearts of heart failure patients implicate a major role for the cardiac epitranscriptome in protein expression. Therefore, addressing this lack of mechanistic insight and understanding the pathomechanisms of yet unexplored epitranscriptomic regulations underlying cardiac remodeling are of major clinical interest. In a first-of-its kind approach, we studied the cardiac epitranscriptome and focused our investigation on N6-methyladenosine (m6A), the most prevalent and functionally relevant chemical modification in mRNA. We discovered that m6A- containing mRNA is significantly increased during ischemic cardiac remodeling, associated with the loss of an m6A demethylase, fat and obesity-associated protein (FTO). We discovered FTO as a critical regulator of m6A methylation in the heart during cardiac remodeling. Post-ischemic loss of FTO is associated with a cascade of biological alterations including increase in m6A methylation, altered mRNA, miRNA and protein expression and diminished myocardial function. Therefore, we hypothesize that ischemic loss of m6A eraser, FTO, increases m6A mRNA methylation resulting in a diminished cardiac function; therefore, FTO gene transfer may rescue cardiac function in the ischemic hearts (Fig1). Our goal is to unravel the complex nature of FTO-modulated m6A-epitrancriptome, which plays a critical role in cardiac homeostasis and cardiac function under ischemia. We propose?for the first time? cardiac epitranscriptome as a highly sensitive, tunable regulatory layer in the pathomechanism of ischemic cardiomyopathy. The aims are: AIM 1: Characterize the dynamics of m6A methylation in mRNA and m6A-signature in post-ischemic mammalian hearts. AIM 2: Determine the role of m6A eraser, FTO in cardiomyocyte and cardiac function. AIM 3: Investigate the mechanisms of m6A function in cardiac mRNA fate and protein expression at the molecular and cellular level. Our finding on the dynamic nature of the cardiac epitranscriptome will open up a new paradigm that will lead to deeper understanding of cardiac remodeling on one hand and innovative therapeutic interventions on the other.